In recent years, an increasing number of patients are suffering from respiratory diseases such as asthma, pulmonary emphysema, chronic bronchitis, etc. One of the most effective therapies for these diseases is oxygen inhalation therapy. In such oxygen inhalation therapy, oxygen gas or oxygen-enriched gas is inhaled by the patient. An oxygen concentrator, liquid oxygen, an oxygen gas cylinder, etc. are known as the oxygen source, among which the oxygen concentrator is mainly used for home oxygen therapy due to its convenience in using and easiness in maintenance.
The oxygen concentrator separates, concentrates and supplies oxygen which exists in air in about 21%. The oxygen concentrator includes a membrane type oxygen concentrator in which a selective oxygen permeable membrane is used and a pressure swing adsorption type oxygen concentrator containing an adsorbent which preferentially adsorbs nitrogen or oxygen. The latter is mainly used because as high concentration as 90% or more of oxygen is obtained.
The pressure swing adsorption type oxygen concentrator can generate highly concentrated oxygen-enriched gas continuously by alternately repeating a pressurization/adsorption step in which nitrogen is adsorbed to an adsorbent and unadsorbed oxygen is obtained under a pressurized condition by supplying air compressed with a compressor to the adsorbent column filled with molecular sieve zeolite such as 5A type, 13X type, Li—X type, etc. as the adsorbent which preferentially adsorbs nitrogen over oxygen and a depressurization/desorption step in which the adsorbent is regenerated by reducing the pressure in the adsorbent column to atmospheric pressure or less, purging nitrogen adsorbed to the adsorbent.
In such an oxygen concentrator, the man-machine user interface such as an operation start/stop switch and oxygen flow rate setting switch is integrated in the main body in order to supply oxygen as prescribed by the physician.